Huawei H12-831_V1.0 Exam With Confidence Using Practice Dumps

When OSPF detects a failure in the network, it performs a series of actions to ensure traffic is rerouted to a valid path. The phases occur in this strict order:

✅ Fault Detection (A)

OSPF routers use Hello packets to maintain neighbor relationships.

If a Hello timeout or link down is detected, the fault is immediately recognized.

✅ LSA Update (B)

Upon detecting a failure, the router generates a new LSA (e.g., a Router-LSA or Network-LSA) and floods it to all other routers in the same area.

This LSA communicates the change in network topology.

✅ Route Calculation (C)

Each router that receives the updated LSAs runs the SPF algorithm to recompute the best path to every destination.

✅ Entry Delivery to the FIB (D)

After recalculating the routes, the router installs the new forwarding entries into the FIB (Forwarding Information Base), allowing data to be forwarded along the new optimal path.

✅ Official Huawei Reference:

" OSPF convergence after a network failure consists of fault detection, LSA flooding, SPF calculation, and updating the FIB. Each step must be completed for traffic to resume correctly on alternate paths. "

— [Huawei HCIA-Datacom Certification Guide – Chapter: OSPF Convergence and SPF Algorithm]

Comprehensive and Detailed In-Depth Explanation:

1. Understanding Route Targets (RT) and Route Distribution in MPLS VPN

MPLS Layer 3 VPNs (L3VPNs) use BGP to distribute VPN routes across multiple Provider Edge (PE) routers.

Each VPN instance (VRF) is configured with Route Targets (RTs) to control which VPN routes are imported/exported.

Route Distinguishers (RDs) are unique per VRF but do not affect route selection.

2. Analyzing VPN1 Configuration

VPN1 is exporting routes with the following Route Targets (vpn-target values):

100:1

200:1

300:1

Remote VPNs will import these routes only if their import RT list matches one of the exported RTs.

3. Matching Exported RTs with Import RTs in Remote VPNs

Remote VPN

Import RTs

Matches VPN1 Exported RTs (100:1, 200:1, 300:1)?

Accepts the Route?

VPN1

100:1

✅ Matches 100:1

✅ Yes

VPN2

200:1, 400:1

✅ Matches 200:1

✅ Yes

VPN3

100:1, 300:1

✅ Matches 100:1, 300:1

✅ Yes

VPN4

500:1

❌ No match

❌ No

✅ VPN1, VPN2, and VPN3 accept the route.

❌ VPN4 does not accept the route because 500:1 is not in the export list of VPN1.

Final Conclusion:

✅ Correct Answer: VPN1, VPN2, and VPN3 will accept the route.

❌ VPN4 does not accept the route because there is no matching RT.

Thus, the correct answer is:

✅ A. VPN1: Import RT=100:1

✅ B. VPN2: Import RT=200:1, 400:1

✅ C. VPN3: Import RT=100:1, 300:1

❌ D. VPN4: Import RT=500:1 (No match, does not accept the route).

OSPFv3 Router-LSAs describe router capabilities, connected links, interface identifiers, neighboring router identifiers, and routing metrics.

The displayed LSA has an originating router ID of 10.0.4.4, while R1 ' s router ID is 10.0.1.1. Therefore, the LSA was not generated by R1.

The Router-LSA contains two transit-network link descriptions, indicating at least two OSPFv3-enabled interfaces.

Its flags show that the originating router is not currently identified as an ASBR.

However, the Router-LSA does not establish that the originating router never generates Network-LSAs. Network-LSAs are originated by Designated Routers (DRs) on applicable multiaccess networks.

Determining whether this router originates a Network-LSA requires additional information about DR election and the relevant network interfaces.

Therefore, statement D is false because the Router-LSA alone does not justify that conclusion.

HCIP-Datacom-Advanced Routing & Switching Technology V1.0 Training Material.pdf

================